ENGLISH ABSTRACT:
Hybrid graft copolymers of polystyrene (PSty) and polydimethylsiloxane macromonomers (PDMS)
were synthesised. PSty-g-PDMS was synthesised employing the grafting through technique via a
conventionally free radical polymerization (FRP) using a polydimethylsiloxane macromonomer. In
this series the amount of PDMS incorporated into the copolymer was varied by varying the
macromonomer to styrene ratios as well as the length of the PDMS side chain. This allows for the
study of the effect that the macromonomer content and the branching length has on the efficiency
of the grafting process. A second series of PDMS-g-PSty was also synthesized where the PDMS
forms the backbone and the PSty the grafts. Two synthetic techniques were employed for the
formation of these polymers. Firstly, the grafting onto approach was used where functional
polystyrene prepolymers with either an allyl or vinyl end-groups were synthesised anionically
(living anionic polymerization) prior to the coupling of a functional prepolymer using a
hydrosilylation reaction with a Karstedt platinum catalyst. This technique was successful and gave
insight to the effect of the polystyrene prepolymer graft length has on the grafting efficiency as well
as the functional groups needed on the PDMS backbone. Furthermore, the effect of the viscosity
(of the PDMS macromonomer) plays on the grafting efficiency was also elucidated. Lastly, the
grafting from approach was employed for the formation of PDMS-g-PSty. ATRP, atom transfer
radical polymerization, of styrene using a bromoisobutyrate functional PDMS macroinitiator was
used for the synthesis of these copolymers. This was accomplished by reacting commercial silane
functional PDMS molecules via a hydrosilylation reaction (using a Karstedt catalyst) with allyl-2-
bromo-2-methyl-propionate to give a PDMS macroinitiator with bromoisobutyrate functional
groups. This will allow for the initiation and growth of polystyrene branches from the PDMS
backbone (employing ATRP with a suitable catalyst and ligand). The formation of the endproduct,
PDMS-g-PSty, via this route proved to be extremely difficult and largely unsuccessful.
Liquid chromatography (LC) at the critical point (LCCC) of polystyrene was used to separate the
graft material from homo-polymers which might have formed as well as from the PDMS
macromonomer. This technique allows for a very fast chromatographic analysis of the grafting
reaction. Under the critical conditions of PSty it was found that the graft copolymer eluted at a
lower retention time than the unreacted macromonomer and PSty homopolymer. Two-dimensional
chromatography, where LCCC (1st dimension) was coupled to size exclusion chromatography (2nd
dimension), was used for the evaluation of the CCD and MMD (molecular mass distribution) of the
graft material. LC was furthermore coupled off-line to FTIR and TEM using an LC interface. LCFTIR
gave insight to the microstructure of the material, whilst LC-TEM gave insight to the
morphological nanostructure of the material.